We have continued to leverage the Adolescent Supplement of the National Comorbidity Survey's (NCS-A) rich information on risk factors to expand the scientific knowledge base that can be used to inform prevention efforts. We published a study of the association between engagement in regular physical activity and adolescent psychiatric disorders (He et al, 2018), and found that physical activity was associated with lower odds of mood disorder and psychological distress, but higher odds of alcohol use disorder and eating disorder. Importantly, some associations were observed only among adolescents who did or did not participate in organized sports. In collaboration with colleagues at Columbia and Johns Hopkins Universities, we published a methodological article that focused on school- and peer-level mechanisms linking neighborhood disadvantage to adolescent substance use and substance use disorder in the NCS-A (Rudolph et al, 2018). The purpose of this paper was to assist public health researchers in choosing between, and implementing, different statistical methods that can be used to study the pathways by which risk factors affect mental health. Additionally, in accordance with NIMH's recent focus on suicide prevention, we also conducted a study of social functioning, including characteristics of friendships, sibling relationships, family cohesion, and parenting style, and its association with suicidal thoughts and suicide attempts among adolescents in the NCS-A (Van Meter et al, 2019). This study took a unique approach by addressing these questions among adolescents with and without mental illness separately. We also investigated patterns of offspring-perceived family environment and their associations with parental bipolar disorder (BD) in a prospective study of adolescents age 12-21 from urban academic medical centers in the U.S. and Australia. We found that maternal BD was associated with offspring perceiving High Maternal Conflict. It may be helpful to support mothers with BD by addressing family functioning, with attention to offspring perceptions of their wellbeing, in clinical care and psychosocial settings (Stapp et al, 2019). We have also continued to study comorbidity between psychiatric disorders and other types of health conditions. In collaboration with researchers at the Mayo Clinic, we published the only nationally-representative study of the links between hypersomnolence and mental health among adolescents (Kolla et al, 2019). We found that adolescents with hypersomnolence were more likely to have behavioral disorders and eating disorders as well as insomnia. This study contributes to our understanding of the complex interrelationships between sleep/wake function and mental health. We have also continued to work on the Philadelphia Neurodevelopmental Cohort Study and conducted a study of comorbidity of headache and migraine with other physical and mental health conditions in youth aged 8-21 (Lateef et al, 2019). We found that youth with migraine were more likely to have specific mental and physical conditions, including respiratory and neurologic conditions as well as anxiety, behavior, and mood disorders. An important aspect of our work is the ability to use population-based studies to inform psychiatric disorder definitions and classification. During the past year we worked with a team of researchers to combine data from 9 community studies in 5 countries, including the Zurich Cohort Study, to assess the validity of the definition of BD (Angst et al, 2019). Our results showed differences between groups in psychiatric disorder comorbidity, although no differences in family history of psychiatric disorder. This study contributes to the ongoing debate in the literature regarding the classification of unipolar mania among psychiatric disorders. In line with our branch's focus on genetic epidemiology, we published two articles pertaining to the future of genetic research in mental health. The first (Arguello et al, 2019) is a report by the Genomics Workgroup of the National Advisory Mental Health Council (NAMHC). This workgroup, convened by the NIMH, is comprised of geneticists and neuroscientists to advise the NAMHC and works to enhance the NIMH's psychiatric genetics research program, prioritize follow-up studies, and provide guidance in many areas relevant to genomics research. The purpose of this article is to assist researchers in creating the most scientifically rigorous and informative research designs possible to maximize progress gained from research funding. The second (Merikangas and Merikangas, 2019) is a commentary describing current challenges, and potential solutions, to the translation of genetic discovery to improve population mental health. This article, written for a wider audience and aims to bring the public health community up to date regarding large-scale population genetic research. Our branch's expertise in the conduct of family studies and statistical genetics has facilitated our collaboration with other researchers in these areas. First, using a community-based longitudinal study of 16-year-old probands who were followed through age 30, we identified clinical characteristics of alcohol use disorders among probands that were associated with the frequency of disorder among first-degree relatives (Farmer et al, 2018). Second, in collaboration with researchers from NIMH, Mount Sinai, Baylor, and Columbia University, we conducted a statistical analysis of the genetic contribution to response to two fast-acting depression treatments, ketamine and scopolamine (Guo et al, 2018). These activities fulfill our ongoing mission to serve the wider research community in using genetic study designs to improve population mental health. Public Health Impact: The investigation of risk factors during development, which the NCS-A makes possible, is extremely important in mental health because many cases of psychiatric disorder first arise during or prior to young adulthood and because brain development is implicated in the etiology of many psychiatric disorders. Our studies of physical activity and sleep in adolescents complement our family study work on the importance of behavioral rhythms in mental health and contribute to scientific understanding of psychiatric disorder etiology and opportunities for prevention. Our continuing mission to help identify the appropriate thresholds and boundaries for defining psychiatric disorders addresses an important current challenge in translating research to improvements in public health, as discussed in our recent commentary. Our branch also continues to serve the broader scientific community by promoting advancement in research questions, study design, and statistical analysis. Future Plans: A current issue in mental health research is the need for transdiagnostic approaches to studying mental illness and brain development. Toward this end, we have continued to be active in the ongoing Child Mind Institute's Healthy Brain Network (HBN) and plan to begin intensive analysis of collected data during the next reporting period. The HBN will serve as a resource for researchers in the field who wish to tackle transdiagnostic research questions related to mental health in children and youth. To further this goal, we have also recently begun work on establishing a Child Mental Health Research Database, which will serve a resource for researchers across the world who are interested in working with data related to youth mental health. We also expect to continue publishing population-based studies related the themes of 1) the intersection between physical and mental health, 2) the relation between health behaviors and psychiatric disorder, and 3) the influence of environmental and social exposures among children and youth.